About the only source I'm aware of for aluminum 216 pistons is Egge Machine, and they think they're made of gold, not aluminum alloy! Original equipment 216 pistons were cast iron. Try an ad in the "parts wanted" forum- - - -somebody's probably got some good used 235 pistons left over from an engine job gathering dust on a shelf somewhere.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!